1. Field of the Invention
The invention is related to the field of data storage, and in particular, to a method and system for managing, storing and providing a plurality of tape cartridges for access to tape drives.
2. Background
A popular device for handling large amounts of information in a data processing system is an automated tape cartridge library. Tape cartridge libraries store and manage large numbers of tape cartridges containing magnetic tape on which data is recorded. Typically, a tape cartridge library is comprised of a plurality of fixed tape cartridge storage locations and at least one read/write tape drive. The tape cartridge storage locations are arranged in predetermined arrays of uniquely identified cells with each cell containing a single tape cartridge. Each of the individual tape cartridges include a computer readable identifying indicia, such as a bar code.
A tape cartridge retrieval/transport mechanism automatically exchanges the individual tape cartridges between their storage locations and the tape drive. Different types of tape cartridge retrieval/transport mechanisms are used to accommodate the various tape cartridge arrangements in different tape cartridge library systems. One example of a tape cartridge retrieval/transport mechanism utilizes a rotatable robotic arm with an optical sensor for selecting and retrieving the correct tape cartridge and transporting the tape cartridge to the one or more tape drives. Another example of a tape cartridge retrieval/transport mechanism is a linear robotic mechanism that moves along an X-Y translation or about a pivot in a rotary motion to select, retrieve and transport tape cartridges to the one or more tape drives. The tape drive is operable to read/write data from or to the magnetic tape in the tape cartridge. A host computer that communicates with a library control unit typically controls operation of the tape library system. In all of these architectures, the tape cartridge retrieval/transport mechanism is a complex mechanism which must translate among the multitude of fixed tape cartridge storage locations, moving in three dimensions to retrieve selected tape cartridges for insertion into the tape drive. The complexity of this tape cartridge retrieval/transport mechanism accounts for a significant component of the cost of the tape cartridge library systems and requires a significant amount of space to implement. Therefore, the cost of a tape cartridge library system cannot be justified in many applications unless there are a large number of tape cartridges that are stored and managed by the tape cartridge library system.
The tape drive is typically mounted within or juxtaposed to the tape cartridge library system and is operable to read/write data from or to the magnetic tape in the tape cartridge. A host computer that communicates with a library control unit and the tape drive(s) typically controls operation of the tape cartridge library system.
Automated tape cartridge library systems, however, suffer from numerous drawbacks. Three major and related drawbacks of these systems are cost, the lack of expandability and the overall size. Unfortunately, simply adding additional tape cartridge storage locations to add capacity to a library system results in an unacceptably slow tape cartridge retrieval and transport response time and additional size. One solution to this problem is the addition of another tape cartridge library system. However, this increases the system size and space required for data storage. Additionally, the load balancing between multiple tape cartridge library systems is often difficult, and in many instances, it is desirable to move data cartridges from one tape cartridge library system to another tape cartridge library system to balance the workload. In this case, a pass through mechanism is utilized to permit the exchange of tape cartridges between multiple tape cartridge library systems. Unfortunately, these pass through systems require that the tape cartridge libraries be specially designed with a common interface. One example of this interface is a common wall between two tape cartridge library systems. The common wall allows for the insertion of tape cartridges into slots in the wall by one tape cartridge library system while the other tape cartridge library system accesses the tape cartridges from the common wall on the other side.
These solutions, while solving one problem, also pose additional problems that result in additional system complexity, expense, and size. For example, the unique identifying information for each tape cartridge is affixed to a face of the tape cartridge that protrudes from a cell when the tape cartridge is stored therein. The pass-through system must therefore remove a tape cartridge from a first tape cartridge library system at a first orientation and rotate the tape cartridge to a second orientation for the second and adjacent tape cartridge library system. These and other problems become more pronounced when still additional tape cartridge libraries are added.
Therefore, there exists a need in the art of data storage for a tape cartridge library system that simplifies the storage and handling of large amounts of information, reduces the size of the system and space required for data storage, while at the same time being scalable, upgradable, and expandable.
The present invention solves the problems outlined above and advances the art by providing an automated tape cartridge autoloader/library system, termed xe2x80x9cautoloader/library systemxe2x80x9d herein. The autoloader/library system comprises at least one read/write tape drive, a tape cartridge picker, a single tape cartridge interface, and at least one of a pair of tape cartridge transport magazines within a compact form factor that fits into a standard library rack mount or cabinet. The autoloader/library system is a complete tape cartridge library that stores, manages, and automatically exchanges a plurality of tape cartridges between the tape drive unit, the single cartridge interface, and the tape cartridge transport magazines. The autoloader/library system can either function as a traditional tape cartridge library system where the plurality of tape cartridges stored in the magazine(s) are managed by the autoloader/library system, or the autoloader/library system can function to present a plurality of scratch (blank) tapes to the tape drive(s) for the writing of data thereon. In this latter application, the magazine functions to queue a plurality of scratch tapes for the tape drive(s) so that data can be written on each of the scratch tapes without the necessity of an operator having to manually load scratch tapes into the tape drive(s).
The autoloader/library system is architected such that the components therein are substantially coplanar and the movement of the picker is limited to simple rotation and optional elevation repositioning to thereby simplify the mechanisms used to implement the autoloader/library system and reduce the cost. The tape cartridge transport magazines are each configured to receive and store a plurality of individual tape cartridges in a horizontal relationship. The tape cartridge transport magazines also transport the individual tape cartridges within the tape cartridge transport magazine so that any one of the tape cartridges can be positioned for selection by the cartridge picker. The cartridge picker does not need to translate in three dimensions as in prior art tape cartridge library systems, but instead is configured to rotate within a stationary picker base to position the cartridge picker to exchange the individual tape cartridges with one of: the tape drive, the tape cartridge transport magazines, and/or the single tape cartridge interface. In the instance where the tape drive component is implemented as a pair of stacked half-height tape drives, the cartridge picker can be elevated to access the second tape drive. The single tape cartridge interface is configured to receive individual tape cartridges from an operator so that the individual tape cartridge can either be stored in one of the cartridge transport magazines or presented to the tape drive for read/write operations and also eject an individual tape cartridge from the autoloader/library system to the operator.
The autoloader/library system is also configured to mechanically and electrically interconnect with other substantially identical autoloader/library systems by stacking multiple autoloader/library systems to provide expandability and scalability as a matter of design choice. Once stacked, the multiple autoloader/library systems could each include their own tape cartridge transport magazines, tape drive, and cartridge picker or could share elements such as tape cartridge transport magazines, tape drives and cartridge pickers. In addition, stacked autoloader/library systems can also share tape cartridges to provide efficient load balancing and operation.
A first advantage of the present autoloader/library system, is the use of transport mechanisms in the tape cartridge transport magazines to position tape cartridges for selection by the cartridge picker. Advantageously, this significantly limits the amount of travel for the cartridge picker to exchange tape cartridges between the tape drive, the magazines and the single cartridge interface. For example, in prior art systems, the robotic cartridge retrieval mechanism was required to move to the fixed location of a desired tape cartridge in a magazine, select the tape cartridge from the magazine, and the robotic cartridge retrieval mechanism then had to move to the location of the tape drive, which operations are time consuming and require the use of complex mechanisms to move the robotic cartridge retrieval mechanism. In contrast, in the autoloader/library system the cartridge picker simply rotates between the tape cartridge transport magazines, the tape drive and the single cartridge interface. Thus, the present autoloader/library system provides fast and efficient exchange of tape cartridges between the magazines, the single cartridge interface, and the tape drive. A second advantage of the present autoloader/library system is the use of the transport mechanisms in the magazines to provide a substantially smaller form factor by reducing the space required for operation of the cartridge picker. A third advantage of the present autoloader/library system is the storage of the tape cartridges in a horizontal relationship within the magazines to facilitate the substantially smaller form factor. A fourth advantage of the present autoloader/library system, is the expandability and scalability provided by stacking multiple autoloader/library systems to expand capacity. A fifth advantage of the autoloader/library system, is the accommodation of individual tape cartridges by the single cartridge interface without interrupting operation of the autoloader/library system. For example, the autoloader/library system can be inventorying the tape cartridges within the magazines, reading and writing data in the tape drive, and be shuttling tape cartridges between the single cartridge interface and the magazines. Additionally, during ejection from the single cartridge interface the tape cartridge is ejected far enough to prevent locking up of the cartridge picker. Finally, once ejected the tape cartridge cannot be reinserted without providing a control input, thus preventing damage to the cartridge picker by a reinsertion when the picker is performing another operation. A sixth advantage of the present autoloader/library system is that the compact form factor measures only three and one half inches in height and fits in a standard library rack mount both individually and when coupled with other similar autoloader/library systems.